An Ru-substituted tris(ethynyl)methyl cation: synthesis, properties, and structure of [{Cp(dppe)Ru(C≡C)}₃C]PF<inf₆C₆H₆

Abstract

The dark blue complex [{Cp(dppe)Ru(C≡C)}3C]PF6 1 (Cp = cyclopentadienyl, dppe = 1,2-bis(diphenylphosphino)ethane) was obtained in 46 % yield by treatment of Ru(C≡CH)(dppe)Cp with CuCl/TMEDA (tetramethylethanediamine), followed by KOH and [NH4]PF6 in acetone; it was accompanied by known complexes {Cp(dppe)Ru}C≡CC≡C{Ru(dppe)Cp} 2 (22 %) and yellow [1,3-{Cp(dppe)Ru}2C4H3]PF6 3 (2.6 %). The structure of the cationic fragment of 1 in its benzene solvate consists of a central planar C attached to three C≡CRu(dppe)Cp fragments. The cation of 3 consists of a cyclobuten-1,3-diyl group bearing two Ru(dppe)Cp groups. The 13C NMR resonance of the central C in 1 is found at δ 66.11. The cyclic voltammogram of 1 contains three irreversible oxidation waves at +0.87, +0.79, and +0.25 V, together with a reversible reduction wave at −1.38 V (versus FeCp2/[FeCp2]+).